Vol. XI · Flavour Plate 5 of 12umami, glutamate, MSG, inosinate, guanylate, synergy, dashi, kombu, katsuobushi, stock, mushrooms, YamaguchiMF

Umami and Synergy.

Kombu alone makes a mild broth; bonito flakes alone, another. Together they taste many times stronger than either. Dashi is a synergy you can measure.

Umami is the taste of free glutamate, an amino acid released as proteins break down in ageing, fermenting and long cooking. Parmesan, ripe tomatoes, soy sauce, fish sauce, miso, kombu, cured ham and long-simmered stocks are rich in it. Monosodium glutamate (MSG) is simply its sodium salt, crystallised: the same glutamate, made by fermentation, and judged safe at normal intakes by food-safety agencies worldwide.

Two nucleotides — inosinate (IMP), plentiful in meat, fish and bonito flakes, and guanylate (GMP), in dried shiitake — have little taste alone but multiply glutamate's. Shizuko Yamaguchi measured the effect in 1967: equal parts of MSG and IMP taste about as strong as many times their weight of MSG alone. That is why so many traditional stocks combine a glutamate source with a nucleotide source: kombu with bonito in dashi, vegetables with bones in stock, tomato with meat, shiitake with chicken. The workshop mixes them.

Below: the umami strength, as the equivalent concentration of MSG alone, of a fixed total of MSG and IMP against the share that is IMP (Yamaguchi's equation), and the strength of the mix you choose.

What you will learn

Explain where glutamate in food comes from.
Describe umami synergy.
Build stocks that combine glutamate and nucleotides.
Treat MSG as an ingredient.

Workshop

Yamaguchi's equation (1967): y = u + 1218 u v, where u and v are the concentrations (g/dL) of MSG and IMP in the mixture and y is the MSG concentration of equal taste. Measured with trained tasters for mixtures up to about 0.1 g/dL; beyond that, perception saturates.

One plus one is sixteen

At 0.05 g/dL in total, a half-and-half mix of MSG and IMP tastes like MSG alone at 0.79 g/dL: 16 times stronger. Even a little IMP does a lot: a broth with 0.05 g/dL of glutamate tastes 7.1 times stronger with just 0.005 g/dL of IMP added. That is the arithmetic of dashi — glutamate from kombu, inosinate from katsuobushi — and of a Western stock built on bones and vegetables, or a Chinese 上汤 of ham, chicken and pork.

Use it in cooking. Pair a glutamate ingredient with a nucleotide one: tomato and anchovy, parmesan and mushroom, soy sauce and chicken, kombu and dried shiitake for a vegetarian dashi. Cook stocks gently so proteins break down without clouding (XXII.1). And treat MSG as an ingredient like salt: a pinch (0.1–0.3 % of the dish) rounds a soup, stir-fry or dressing; it contains about a third of the sodium of salt, so using some in place of part of the salt can lower sodium while keeping the dish tasting seasoned.

At the stove

Make a cup of kombu water (a 5 cm square soaked 30 minutes, warmed to just below simmering) and a cup of water infused with bonito flakes. Taste each, then mix half of each. The mix is far more savoury than either.

Kikunae Ikeda patented the manufacture of MSG in 1908 and founded the company that still makes Ajinomoto; the "Chinese restaurant syndrome" scare of 1968 was not borne out by later double-blind studies.

Terms

Glutamate: The amino acid whose free form tastes of umami.
MSG: Monosodium glutamate: glutamate as a crystalline sodium salt.
Inosinate and guanylate: Nucleotides from meat and fish (IMP) and mushrooms (GMP) that multiply glutamate's taste.
Dashi: Japanese stock of kombu and katsuobushi.

Umami is free glutamate; combined with inosinate or guanylate it tastes many times stronger — the logic of dashi and stock.

Sources

S. Yamaguchi, "The synergistic taste effect of monosodium glutamate and disodium 5'-inosinate", J. Food Sci. 32, 1967: y = u + 1218·u·v, concentrations in g/dL.
A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.